This project provides statistics and analyses of epidemiologic and photobiologic data relevant to the etiology of skin cancer, including malignant melanoma. Through these studies, NCI provides research in response to Public Law 95-95 (Amendment to the Clean Air Act) and the federal stratospheric ozone protection policy program. Recently, worldwide non-aerosol production of cholofluorocarbons has increased, and significant depletions of ozone and increases of solar untraviolet radiation, specifically UVB (290nm-320nm) exposure on earth, accompanied by increased incidence in skin cancer have been predicted. To evaluate the role of UVB, we calculate incidence rates for groups at high and low risk of skin cancer across geographic areas of relatively high and low UVB exposure within the United States. Biologic amplification factors (BAF), i.e., the relative change in incidence due to specified relative changes (usually 10% or 1%) in UVB dose, are estimated by sex and cell type. As we measure and monitor direct measurements of the amounts of biologically effective solar ultraviolet (i.e., nonionizing radiation capable of producing skin erythema), we provide improved estimates of the BAF. Our latest estimates indicate that a 10 percent increase in UVB may result in a 16 to 20 percent increase in basal cell carcinomas (BCC), a 20 to 40 percent increase in squamous cell carcinomas (SCC), and a 6 to 10 percent increase in malignant melanomas of the skin. Annually, one-half million caucasian Americans are expected to develop at least one new skin cancer. For those living in sunny or southern U.S. regions, the lifetime expectancy of developing skin cancer may be over 30 percent; in contrast, only 12 percent of those living in northern regions may develop this disease. The lifetime probability of developing skin melanoma is much lower, varying betwen 0.6 percent and 1.2 percent across comparable geograhic locations.